Another multiheme protein, hydroxylamine oxidoreductase, abundantly produced in an anammox bacterium besides the hydrazine-oxidizing enzyme

Structural Basis of Biological NO Generation by Octaheme Oxidoreductases

“…These findings strongly suggested that the oxidation of hydroxylamine to NO was the distinctive physiological reaction of kustc1061. The kustc1061 catalytic constants were in the same range as those reported for not well defined, homologous enzymes of the anammox bacteria Brocadia anammoxidans and strain KSU-1 (Table 2) (49,50). NeHAO oxidized hydroxylamine and hydrazine at 6-and 9-fold higher maximal rates, respectively.…”

Why Orange Guaymas Basin Beggiatoa spp. Are Orange: Single-Filament-Genome-Enabled Identification of an Abundant Octaheme Cytochrome with Hydroxylamine Oxidase, Hydrazine Oxidase, and Nitrite Reductase Activities

“…A protein classified as an HAO/ HZO (23,24) accounted for as much as 9% of the total soluble protein in a "Candidatus Brocadia anammoxidans" enrichment, and an HAO accounting for 7% of the total protein was purified from a cell extract of an anaerobic ammonia-oxidizing sludge dominated by strain KSU-1 (24). The functions of these proteins are not known, although they are considered to play a role in anammox.…”

“…All reactions were performed in triplicate and prepared in an anaerobic Coy Chamber. The hydroxylamine and hydrazine assay solutions consisted of 3.0 ml of 100 mM potassium phosphate buffer (pH 8.0) containing 1.2 mM MTT, 2.0 mM PMS, and 1.5 mM either hydrazine or hydroxylamine (22)(23)(24). The reactions were initiated by the addition of 100 l of enzyme solution (3.1-ml total volume), and the progress of the reactions was monitored spectrophotometrically by collecting spectra every minute for 10 min.…”

High-cell-density cultivation of <i>Nitrosomonas europaea</i> in a membrane bioreactor for performing protein purification and characterization studies

“…The high-cell-density culture was used for performing protein purification and characterization to demonstrate its utility for investigating the functions of specific proteins in cells cultivated using this culture. In the present study, we partially purified N. europaea hydroxylamine oxidoreductase (HAO), a soluble octahaem cytochrome c protein, by using a method described previously (Shimamura et al, 2008). N. europaea oxidizes ammonia to hydroxylamine and hydroxylamine to nitrite by using ammonia monooxygenase and HAO, respectively (Arp et al, 2007).…”